Bombardier's latest proposal would enroll new hires in a defined contribution pension plan instead of the current defined benefit plan, and workers who started after May 2010 would lose their post-retirement benefits, Dias said.

Unclear is how deeply any strike will affect Bombardier's production, including large orders of subway, light rail, and streetcar vehicles for the Greater Toronto Area, as well as a related light rail transit order for the Regional Municipality of Waterloo.

Toronto Transit Commission (TTC) spokesman Brad Ross told local media TTC still plans to introduce Bombardier Flexity streetcars into revenue service on Aug. 31, regardless of the number of streetcars TTC has on hand by that time.